JP2004253168A - Bipolar battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-reliability bipolar battery capable of forming an electrolyte sealing part while keeping a distance between collector foil pieces, and allowing the electrolyte sealing part to double as electrical insulation between electrodes, in a bipolar battery composed by serially connecting cell layers in the battery. <P>SOLUTION: In relation to a bipolar lithium ion secondary battery composed by stacking, by interposing an electrolyte layer, a plurality of bipolar electrodes each having a positive electrode formed on one surface of a collector and a negative electrode formed on the other surface thereof, this bipolar battery is so structured that spacers 23 each used for keeping the distance between the electrodes are installed in the electrolyte sealing parts on the electrode side surfaces. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bipolar battery in which a positive electrode active material and a negative electrode active material are arranged on both sides of a current collector, and unit cell layers are connected in series in the battery, and more specifically, compared to a polymer solid electrolyte. And a bipolar battery using a polymer gel electrolyte having excellent ionic conductivity.
[0002]
[Prior art]
In recent years, reduction of carbon dioxide emission has been urgently required for environmental protection. The automobile industry is expected to reduce carbon dioxide emissions through the introduction of electric vehicles (EVs) and hybrid electric vehicles (HEVs), and is keen to develop secondary batteries for motor drives, which are key to their practical use. Is being done. As a secondary battery, attention has been focused on a lithium ion secondary battery capable of achieving high energy density and high output density. However, in order to apply it to an automobile, it is necessary to use a plurality of secondary batteries connected in series in order to secure a large output.
[0003]
However, when a battery is connected via the connection, the output decreases due to the electrical resistance of the connection. Also, batteries with connections have spatial disadvantages. That is, the connection portion lowers the output density and energy density of the battery.
[0004]
As a solution to this problem, a bipolar battery in which a positive electrode active material and a negative electrode active material are arranged on both sides of a current collector has been developed.
[0005]
Among them, a bipolar battery using a polymer solid electrolyte containing no solution as an electrolyte has been proposed (for example, see Patent Document 1). According to this, since no solution (electrolyte solution) is contained in the battery, there is no need to worry about liquid leakage or gas generation, and a highly reliable bipolar battery that does not require a hermetically sealed structure can be provided. is there. However, the ionic conductivity of a polymer solid electrolyte is lower than that of a separator in which an electrolyte is impregnated as an electrolyte (hereinafter, simply referred to as a solution electrolyte) or a gel electrolyte. At present, the density is not sufficient, and it has not reached the stage of practical use, and further improvement in ionic conductivity is expected.
[0006]
On the other hand, a bipolar battery using an electrolyte having an electrolytic solution has been proposed (for example, see Patent Document 2). If an electrolyte having an electrolytic solution, particularly a gel electrolyte, is used, it is expected to be a bipolar battery which is excellent in ionic conductivity and sufficiently obtains the output density and energy density of the battery, which is the closest to the practical use stage.
[0007]
[Patent Document 1]
JP 2000-100471 A
[Patent Document 2]
JP-A-11-204136
[0008]
[Problems to be solved by the invention]
However, when attempting to configure a bipolar battery using a solution-based electrolyte or a polymer gel electrolyte having a high ratio of electrolyte solution using a separator impregnated with the electrolyte solution in the electrolyte layer, the electrolyte solution is pressed from the electrolyte portion by pressing or the like. There is a danger that a liquid junction (short circuit) may occur between the unit cell layers due to seepage. That is, unlike a conventional lithium-ion battery which is not a bipolar type, unlike a lithium-ion battery in which stacked electrodes in a battery are connected in parallel, a bipolar battery in which unit cell layers stacked in a battery are connected in series is a unit cell. When the collector foils between the layers are in mechanical contact with each other or in contact with each other via the electrolytic solution, an electrical short circuit (or an ionic short circuit; liquid junction) occurs. To prevent this, it is necessary to form an electrolyte seal around the unit cell layer.
[0009]
As a method of forming the seal portion, a method of laminating the electrodes and then pouring a resin around the electrodes can be considered.
[0010]
However, the metal foil used for a normal current collector has a thickness of about 10 to 20 μm, and the interval between the foils is also about 100 μm. Therefore, when an attempt is made to inject a high-viscosity resin precursor there. The foils may come into contact with each other due to the pressure of the resin precursor.
[0011]
When the foils come into contact with each other, the unit cell layers are electrically short-circuited. To prevent this, an insulation treatment is applied around the current collector foil on which the electrodes are formed (an electrolyte seal must be separately formed). Then, an extra structure increases.
[0012]
Therefore, an object of the present invention is to form an electrolyte seal portion while maintaining a gap between current collector foils in a bipolar battery in which unit cell layers are connected in series in the battery. An object of the present invention is to provide a highly reliable bipolar battery that can also serve as electrical insulation between electrodes.
[0013]
[Means for Solving the Problems]
According to the present invention, a bipolar electrode in which a positive electrode is formed on one surface of a current collector and a negative electrode is formed on the other surface is formed by interposing a separator (solution electrolyte) impregnated with an electrolyte or a polymer gel electrolyte. In a bipolar lithium ion secondary battery stacked in series,
A bipolar battery, wherein a spacer for maintaining a space between electrodes is provided in an electrolyte seal portion on a side surface of the electrode.
[0014]
【The invention's effect】
In the bipolar battery of the present invention, since the spacer for maintaining the interval between the electrodes is provided in the electrolyte seal around the current collector foil on which the electrodes are formed (side surface of the electrodes), the periphery of the unit cell layer is provided. When the electrolyte seal portion is formed, even if a resin is poured around the electrodes after laminating the electrodes, it is possible to prevent the foils from contacting each other. Thereby, the electrolyte seal portion can be formed by pouring or dipping the resin (precursor). Therefore, leakage of the electrolyte solution from the solution electrolyte or the polymer gel electrolyte can be easily and effectively prevented. Therefore, it is possible to prevent a liquid junction (short circuit) between the unit cell layers, to provide a compact bipolar battery having excellent ionic conductivity and excellent battery characteristics such as charge and discharge characteristics. Therefore, it has high reliability, can maintain excellent energy density and power density, and is a useful power source in various industries. This can prevent the foils from coming into contact with each other when forming the electrolyte seal portion even in a bipolar battery using a solid polymer electrolyte, and thus can provide the same effect.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0016]
The bipolar battery according to the present invention includes a bipolar electrode in which a positive electrode is formed on one surface of a current collector and a negative electrode is formed on the other surface. In a bipolar lithium ion secondary battery stacked in series with a plurality of
A spacer is provided in the electrolyte seal portion on the side surface of the electrode to keep a space between the electrodes.
[0017]
Further, the method for manufacturing a bipolar battery according to the present invention is characterized in that, when laminating electrodes, a spacer is arranged around the electrodes, and then a resin is injected around the electrodes to form an electrolyte seal portion. It is. Hereinafter, the bipolar battery of the present invention will be described together with a method of manufacturing the characteristic portion thereof.
[0018]
In the present invention, the contact between the foils (the current collector) can be prevented, so that the electrolyte seal portion (the portion where the resin for the electrolyte seal is held) can be easily and reliably formed, and A liquid junction (short circuit) due to leakage can also be prevented.
[0019]
The outline of the basic configuration of the bipolar battery according to the present invention will be briefly described with reference to FIGS. FIG. 1 is a schematic cross-sectional view schematically showing the structure of a bipolar electrode constituting a bipolar battery, and FIG. 2 is a schematic sectional view showing the structure of a unit cell layer constituting a bipolar battery. FIG. 3 is a schematic cross-sectional view, FIG. 3 is a schematic cross-sectional view schematically showing the entire structure of a bipolar battery, and FIG. 4 is a diagram in which a plurality of unit cell layers stacked in a bipolar battery are connected in series. FIG. 1 shows a schematic diagram conceptually (in symbolic form) of what happens.
[0020]
As shown in FIGS. 1 to 4, the bipolar electrode 5 (see FIG. 1) in which the positive electrode layer 2 is provided on one surface of one current collector 1 and the negative electrode layer 3 is provided on the other surface is connected to the electrolyte. The electrode layers 2 and 3 of the bipolar electrode 5 adjacent to each other with the layer 4 interposed therebetween are opposed to each other. That is, in the bipolar battery 11, a plurality of bipolar electrodes (electrode layers) 5 having the positive electrode layer 2 on one surface of the current collector 1 and the negative electrode layer 3 on the other surface are provided via the electrolyte layer 4. It is composed of an electrode laminate (bipolar battery body) 7 having a laminated structure. The electrodes 5a and 5b of the uppermost layer and the lowermost layer do not have a bipolar electrode structure, but have a structure in which an electrode layer (positive electrode layer 2 or negative electrode layer 3) on only one side required for the current collector 1 (or terminal plate) is formed. I have.
[0021]
Also, the uppermost and lowermost electrodes 5a and 5b of the electrode stack 7 in which a plurality of such bipolar electrodes 5 and the like are stacked need not have a bipolar electrode structure, and are necessary for the current collector 1 (or terminal plate). A structure in which only one electrode layer (the positive electrode layer 2 or the negative electrode layer 3) is provided (see FIG. 3). In the bipolar battery 11, the positive and negative electrode leads 8, 9 are respectively joined to the current collectors 1 at the upper and lower ends.
[0022]
The number of laminations of the bipolar electrode is adjusted according to a desired voltage. If a sufficient output can be ensured even if the thickness of the sheet-shaped battery is made as thin as possible, the number of times of laminating the bipolar electrodes may be reduced.
[0023]
Further, in the bipolar battery 11 of the present invention, in order to prevent external impact and environmental degradation during use, the electrode laminate 7 is sealed in a battery exterior material (exterior package) 10 under reduced pressure, and the electrode leads 8, It is preferable to adopt a structure in which 9 is taken out of the battery exterior material (exterior package) 10 (see FIGS. 3 and 4). From the viewpoint of weight reduction, conventionally known batteries such as a polymer-metal composite laminate film such as an aluminum laminate pack in which a metal (including an alloy) such as aluminum, stainless steel, nickel and copper is coated with an insulator such as a polypropylene film; A part or all of the peripheral portion is joined by heat fusion using an exterior material, thereby housing and laminating the electrode laminate 7 under reduced pressure (sealing), and attaching the electrode leads 8 and 9 to the battery exterior material 10. It is preferable to adopt a configuration taken out to the outside. The basic configuration of the bipolar battery 11 can be said to be a configuration in which a plurality of stacked unit cell layers (single cells) 6 are connected in series, as shown in FIG. The bipolar battery of the present invention is used for a bipolar lithium ion secondary battery in which charging and discharging are mediated by movement of lithium ions. However, this does not prevent application to other types of batteries as long as effects such as improvement in battery characteristics can be obtained.
[0024]
As described above, the present invention is characterized in that a spacer for maintaining a space between electrodes is provided in the electrolyte seal portion on the side surface of the electrode. More specifically, as shown in FIG. 5, a spacer 23 for maintaining a space between the electrodes 5 (the current collectors 1) is provided in an electrolyte seal portion 21 formed on a side surface of the bipolar electrode 5. (See FIG. 5B). Hereinafter, the description will focus on the electrolyte seal portion and the spacer, which are characteristic portions of the present invention.
[0025]
[Electrolyte seal part]
The electrolyte seal portion (hereinafter, also referred to as an insulating layer) is provided for the purpose of preventing current collectors from coming into contact with each other, leaking out of the electrolyte, and short-circuiting due to slight irregularities at the ends of the laminated electrode. , Formed around each electrode.
[0026]
In the present invention, when forming the electrolyte seal portion, the interval between the electrodes is maintained in the electrolyte seal portion for the purpose of preventing the terminals from contacting each other due to compression by the viscous sealing resin and causing a short circuit. Spacers are provided.
[0027]
Conventionally, in a bipolar battery using a solution electrolyte or a polymer gel electrolyte as an electrolyte layer, a positive electrode layer is formed using one type of positive electrode material on one side of a current collector, and one type of negative electrode material is formed on the opposite side. To form a negative electrode layer to form a bipolar electrode, and stack them with a polymer gel electrolyte (layer) interposed therebetween. Therefore, the electrolyte contained in the solution electrolyte or the polymer gel electrolyte may ooze out and come into contact with the electrolyte of another unit cell layer to cause a short circuit (liquid junction). In order to prevent this, as shown in FIG. 9, the present inventors need to form an electrolyte seal around the unit cell layer. As a method of forming the seal, from the viewpoint of simplifying the manufacturing process, As shown in FIG. 9B, as a method of pouring a resin around the electrodes of the electrode laminate 7 after laminating the electrodes, the periphery of the electrodes of the electrode laminate 7 is immersed in a resin precursor 31 in a resin tank. Tried. However, since the metal foil used for the normal current collector 1 has a thickness of about 10 to 20 μm and an interval between the foils of about 100 μm, the high-viscosity resin precursor 31 is immersed therein. 9C, the current collector 1 foils around the electrodes of the electrode laminate 7 may come into contact with each other due to the pressure (compression) of the resin precursor 31 as shown in FIG. 9C. If the foils on the peripheral edge of the current collector 1 come into contact with each other, the cell layers are electrically short-circuited. If an insulating treatment is performed around the electrode foil to prevent the short-circuit, an extra structure increases. Therefore, in the present invention, as described below with reference to the drawings, when laminating electrodes, a spacer is arranged around the electrodes, and thereafter, a resin is injected around the electrodes to form an electrolyte seal portion. This has solved the above problems. Here, FIG. 5 is a schematic plan view and a schematic side view showing a typical electrode used in the bipolar battery of the present invention, schematically showing a state where spacers are arranged around the electrode.
[0028]
As shown in FIG. 5, the electrode 5 used in the bipolar battery of the present invention has a positive electrode 2 formed on one surface of a current collector 1 and a negative electrode (not shown) formed on the other surface. Further, a plurality of spacers 23 are arranged around the electrode 5, that is, outside the application surface 5 a of the electrode (the positive electrode 2 or the negative electrode 3) 5.
[0029]
Here, the shape of the spacer 23 disposed around the electrode 5 may be any shape as long as it can prevent contact between the electrodes, and is not particularly limited. For example, a discontinuous body such as a cylindrical shape, a polygonal prism shape such as a triangle or a square as shown in FIG. 5, a spherical shape, an elliptical shape, or the like, and a continuous body such as a non-woven fabric shown in FIG. And these may be used in an appropriate combination.
[0030]
Also, the size of the spacer 23 disposed around the electrode 5 is not particularly limited as long as it can prevent contact between the electrodes. For example, in the case of a discontinuous body having a cylindrical shape or the like, as shown in FIG. 7, when forming the electrolyte seal portion 21, the width W of the electrolyte seal portion 21 is set so that the spacer is completely taken into the seal portion. ₁ Spacer width W ₂ It is desirable to keep the size and the interval such that the resin precursor for forming the seal portion can be wrapped around the spacer, in particular, behind the spacer (the hatched portion in FIG. 7). When the spacer 23 is a continuous body 23a as shown in FIG. 6, the size and the interval of the space openings 25 of the continuous body 23a are changed to the space openings 25 of the continuous body 23a by the resin for the electrolyte seal portion. What is necessary is just to make it possible to sufficiently fill the precursor by immersion, injection or the like so that the sealing property can be maintained. In the case of a continuous body such as a nonwoven fabric, the ratio is such that the sealing resin is impressed with the continuous body, and as a result, it can be said that the size is substantially the same as the electrolyte seal portion. The width W of the continuum (including the non-woven fabric, etc., in addition to the one shown in FIG. 6) ₃ May be set so as to be approximately the same width as the electrolyte seal portion. The width W of the continuum 23a ₃ Is the width W of the electrolyte seal portion ₁ It is desirable that the width is substantially the same as the width W of the electrolyte seal portion from the viewpoint of the intended use of the spacer. ₁ There is no problem if it is smaller.
[0031]
The thickness (height) of the spacer 23 is only required to prevent contact between the electrodes (the current collector foil), and as shown in FIG. When the spacer 23 is disposed, the height may be substantially equal to the height between the electrodes (the current collector foil), but the upper and lower two spacers are overlapped (laminated) between the electrodes. Is also good. When overlapping, the thicknesses of the upper spacer and the lower spacer may be the same or different. Here, the height corresponding to between the electrodes corresponds to the thickness of the positive electrode layer, the negative electrode layer, and the electrolyte layer (see FIG. 2). If necessary, another spacer may be interposed between the upper and lower spacers. In particular, from the viewpoint of reducing the number of spacer members and simplifying the manufacturing process, it is desirable to dispose the spacers 23 having a height corresponding to between electrodes.
[0032]
In addition, when a discontinuous body is used as the spacer 23 provided around the electrode 5, even when the spacer 23 is installed at the same position (place) when viewed from the side in FIG. It is not particularly limited, for example, it may be installed at a different position.
[0033]
The number of discontinuous bodies used as the spacers 23 depends on the size of the spacers, but is not particularly limited as long as it can prevent contact between electrodes. Therefore, it is preferable that the number of installation is as small as possible within a range satisfying the above requirements.
[0034]
In addition, when a discontinuous body is used as the spacer 23, the installation length is, as shown in FIG. 5 (a), surely installed around the four sides of the current collector from end to end. Even if it does not need to be installed from the end to the end, it may be shorter as long as it can prevent contact between the electrodes.
[0035]
Any material can be used as the material of the spacer as long as it is a material capable of preventing contact between electrodes and preventing liquid junction (short circuit), such as insulation, chemical resistance (particularly alkali resistance), and heat resistance. (Battery operating temperature), etc., which are lightweight, excellent in processability, and excellent in compatibility (adhesion, wettability) with the precursor of the resin for the electrolyte sealing portion, such as polyethylene, polypropylene, Polytetrafluoroethylene, polyester, and the like can be suitably used, but are not limited thereto.
[0036]
Further, the spacer 23 may be installed around the electrode only by temporarily fixing it with glue or the like, for example. Further, it can be installed (bonded) by a conventionally known method such as a chemical bonding method using an adhesive, a thermal fusion method, and a thermocompression bonding method, and is not particularly limited. When an adhesive is used, it is desirable to use a material having insulation properties, chemical resistance (alkali resistance), and the like required for the spacer material and the resin for the electrolyte seal portion. However, in the case of a nonwoven fabric or the like, it may be merely inserted (sandwiched). This is because the nonwoven fabric is then impregnated with the resin for the sealing portion and cured, whereby the nonwoven fabric can be firmly fixed around the electrodes.
[0037]
In addition, there is no particular limitation on the timing of the installation of the spacer, such as before or after forming (printing and applying) the positive electrode or negative electrode layer.
[0038]
Next, as shown in FIG. 8, the electrolyte seal portion 21 provided with the spacer is immersed in the sealing resin precursor 31 (see FIGS. 8 and 9 for comparison), and then cured. The sealing resin 21 is formed by injecting a sealing resin. The spacer 23 can also be considered as a part of the sealing resin of the electrolyte seal part 21.
[0039]
As shown in FIGS. 5A and 7, the electrolyte seal portion 21 formed by injecting and curing the sealing resin is formed from the viewpoint of preventing the electrolyte solution from seeping out from the electrolyte layer. 7 must be formed all around the electrode side surface. The width W of the electrolyte seal portion 21 ₁ It is desirable from the viewpoint of battery characteristics to reduce the value within a range where a sealing effect can be obtained. Therefore, the width W of the electrolyte seal portion 21 ₁ With a thickness of about 5 mm to 2 cm, a sufficient sealing effect can be obtained even in consideration of securing the installation of the spacer.
[0040]
In the case where the continuous body 23a without the opening 25 is provided in the spacer 23, a gap may be formed at a joint portion between the spacers, and thus the sealing portion 21 is formed by injecting a resin into such a gap. It is desirable to ensure the sealing performance of the entire periphery of the electrode side surface of the electrode laminate 7.
[0041]
In the present invention, also in the case where a solid polymer electrolyte is used for the electrolyte layer, the electrodes may be brought into contact with each other due to vibration or impact during battery assembly or during use. It is desirable to adopt a battery configuration suitable for the operation. In this case, since the electrolyte does not seep out, the electrolyte seal portion 21 does not necessarily need to be sealed with a resin or the like, and may be provided only with a spacer. However, as described above, the electrolyte seal portion 21 It may be sealed with a sealing resin.
[0042]
The material for the electrolyte sealing portion (insulating layer) 21 on the side surface of the electrode includes insulating properties, sealing properties against an electrolytic solution (alkaline solution) from the electrolyte layer, alkali resistance, and sealing properties against moisture permeation from the outside (sealing). ), And is not particularly limited as long as it has heat resistance at a battery operating temperature. For example, a resin selected from silicon, epoxy, urethane, polybutadiene, polypropylene, polyethylene, paraffin wax, etc. (Including rubber). These resins have excellent sealing properties (liquid tightness), chemical resistance (alkali resistance), durability / weather resistance, heat resistance, etc., and can effectively prevent the electrolyte solution from seeping out of the electrolyte layer. It is possible to prevent a liquid junction (short circuit) due to oozing out of the electrolytic solution for a long period of time, and to flow the resin precursor around the electrode of the electrode laminate 7 as a resin precursor, whereby the installed space is reduced. Is easily adjusted to such a viscosity that it can be completely taken into the seal portion. Epoxy resins are preferred from the viewpoints of corrosion resistance, chemical resistance, ease of production (film-forming properties), economy, and the like.
[0043]
In the bipolar battery of the present invention using the electrode laminate 7 in which the spacer 23 for maintaining the interval between the electrodes is provided in the electrolyte seal portion 21 on the side surface of the electrode, the spacer 23 acts around the electrode. Since the electrodes can be formed without contact between the electrodes when the resin precursor is injected, an electrical short circuit between the electrodes can be prevented. Further, since the electrolyte seal portion 21 including the spacer can be formed on the entire periphery of the electrode side surface, the electrolyte contained in the electrolyte layer 4 can be effectively prevented from seeping out of the electrolyte seal portion 21. Therefore, it is possible to provide a high-quality bipolar battery that does not come into contact with the electrolytic solution of the other unit cell layer 6 and has high safety without causing a short circuit (liquid junction).
[0044]
The above has been mainly described with respect to the constituent part in which the spacer for maintaining the interval between the electrodes is provided in the electrolyte seal part on the side of the electrode, which is the constituent element of the characteristic part of the bipolar battery according to the present invention. However, other components of the bipolar battery of the present invention are not particularly limited, and can be widely applied to conventionally known bipolar batteries.
[0045]
Hereinafter, the bipolar battery of the present invention will be briefly described focusing on other components other than the above [electrolyte seal portion], but it is needless to say that the present invention should not be limited to these components.
[0046]
[Current collector]
The current collector that can be used in the present invention is not particularly limited, and a conventionally known current collector can be used. For example, aluminum foil, stainless steel foil, a clad material of nickel and aluminum, copper and aluminum Or a plating material of a combination of these metals is preferably used. Alternatively, a current collector in which aluminum is coated on a metal surface may be used. In some cases, a current collector in which two or more metal foils are bonded may be used. It is preferable to use an aluminum foil as a current collector from the viewpoints of corrosion resistance, ease of production, economy, and the like.
[0047]
The thickness of the current collector is not particularly limited, but is usually about 1 to 100 μm.
[0048]
[Positive electrode layer]
The positive electrode layer contains a positive electrode active material. In addition to this, a conductive aid for enhancing electron conductivity, a lithium salt for improving ionic conductivity, a binder, a polymer electrolyte, and the like may be included, but when a polymer gel electrolyte is used for the electrolyte layer, It is sufficient that a conventional binder for binding the positive electrode active material fine particles to each other, a conductive auxiliary agent for enhancing electron conductivity, and the like are included. You don't have to. Even when a solution electrolyte is used for the electrolyte layer, the positive electrode layer may not contain a host polymer as a raw material of the polymer electrolyte, an electrolytic solution, a lithium salt, or the like.
[0049]
Among these, as the positive electrode active material, a composite oxide of a transition metal and lithium (lithium-transition metal composite oxide), which is also used in a solution-based lithium ion battery, can be used. Specifically, LiCoO ₂ Li-Co based composite oxides such as LiNiO ₂ Li-Ni based composite oxide such as spinel LiMn ₂ O ₄ Li-Mn based composite oxides such as LiFeO ₂ Li.Fe-based composite oxides such as In addition, LiFePO ₄ Phosphoric acid compounds and sulfuric acid compounds of transition metals and lithium; ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , MoO ₃ Transition metal oxides and sulfides such as PbO ₂ , AgO, NiOOH and the like.
[0050]
In order to reduce the electrode resistance of a bipolar battery, it is preferable to use a positive electrode active material having a particle size smaller than a particle size generally used in a solution type lithium ion battery. Specifically, the average particle diameter of the positive electrode active material fine particles is preferably 0.1 to 5 μm.
[0051]
Examples of the conductive assistant include acetylene black, carbon black, and graphite. However, it is not limited to these.
[0052]
As the binder, polyvinylidene fluoride (PVDF) or the like can be used. However, it is not limited to these.
[0053]
The polymer gel electrolyte is a solid polymer electrolyte having ion conductivity, as defined above, containing an electrolyte solution usually used in lithium ion batteries. And the like in which a similar electrolyte is held in a polymer skeleton having no polymer.
[0054]
Here, the electrolyte solution (electrolyte salt and plasticizer) contained in the polymer gel electrolyte may be any one that is usually used in a lithium ion battery. ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ Acid anion salts such as LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ Cyclic carbonates such as propylene carbonate, ethylene carbonate and the like containing at least one lithium salt (electrolyte salt) selected from organic acid anion salts such as N; chains such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate Ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane; lactones such as γ-butyrolactone; nitriles such as acetonitrile; Esters such as methyl propionate; amides such as dimethylformamide; and organic solvents (plasticizers) such as aprotic solvents in which at least one or more selected from methyl acetate and methyl formate are mixed. You can use what you used However, it is not limited to these.
[0055]
Examples of the solid polymer electrolyte having ion conductivity include known solid polymer electrolytes such as polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.
[0056]
Examples of the polymer having no lithium ion conductivity used for the polymer gel electrolyte include polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA). it can. However, it is not limited to these. Since PAN, PMMA, and the like fall into the category of having little ionic conductivity, they can be the above-mentioned polymers having ionic conductivity, but are used here as polymer gel electrolytes. It is exemplified as a polymer having no lithium ion conductivity.
[0057]
Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ Inorganic acid anion salts such as Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ Organic acid anions such as N, and mixtures thereof can be used. However, it is not limited to these.
[0058]
The ratio (mass ratio) between the host polymer and the electrolyte in the polymer gel electrolyte may be determined according to the purpose of use and the like, but is in the range of 2:98 to 90:10. That is, leakage of the electrolyte from the electrolyte material in the positive electrode layer can be effectively sealed by adopting the configuration of the present invention. Therefore, the battery characteristics can be given a relatively high priority also in the ratio (mass ratio) between the host polymer and the electrolytic solution in the polymer gel electrolyte.
[0059]
The amount of the positive electrode active material, conductive auxiliary agent, binder, polymer electrolyte (host polymer, electrolyte solution, etc.), and lithium salt in the positive electrode layer depends on the intended use of the battery (output-oriented, energy-oriented, etc.) and ionic conductivity. The decision should be taken into account. For example, when using a gel electrolyte for the electrolyte layer, if the blending amount of the polymer electrolyte in the positive electrode layer is too small, the ion conduction resistance and ion diffusion resistance in the positive electrode layer increase, and the battery performance decreases. I will. On the other hand, if the blending amount of the polymer electrolyte in the positive electrode layer is too large, the energy density of the battery decreases. Therefore, a polymer gel electrolysis mass that meets the purpose is determined in consideration of these factors.
[0060]
The thickness of the positive electrode layer is not particularly limited, and should be determined in consideration of the intended use of the battery (e.g., emphasis on output, energy, etc.) and ionic conductivity, as described for the blending amount. The thickness of a general positive electrode layer is about 10 to 500 μm.
[0061]
[Negative electrode layer]
The negative electrode layer contains a negative electrode active material active material. In addition, a conductive auxiliary agent for improving electron conductivity, a binder, a polymer electrolyte (such as a host polymer and an electrolyte), and a lithium salt for improving ionic conductivity may be included. In the case of using a polymer gel electrolyte, it is sufficient that a conventionally known binder that binds the negative electrode active material fine particles to each other, a conductive auxiliary agent for increasing electron conductivity, and the like are included, and a host polymer as a raw material of the polymer electrolyte is used. , Electrolyte and lithium salt may not be contained. Even when a solution electrolyte is used for the electrolyte layer, the negative electrode layer may not contain a host polymer as a raw material of the polymer electrolyte, an electrolytic solution, a lithium salt, or the like. Except for the type of the negative electrode active material, the content is basically the same as that described in the section of “Positive electrode layer”, and thus the description is omitted here.
[0062]
As the negative electrode active material, a negative electrode active material used in a solution-type lithium ion battery can be used. Specifically, carbon, a metal oxide, a lithium-metal composite oxide, or the like can be used, but carbon or a lithium-transition metal composite oxide is preferable. By using these, a battery excellent in capacity and output characteristics (for example, battery voltage can be increased) can be configured. As the lithium-transition metal composite oxide, for example, a lithium-titanium composite oxide or the like can be used. As the carbon, for example, graphite, graphite, acetylene black, carbon black, and the like can be used.
[0063]
[Electrolyte layer]
In the bipolar battery of the present invention, from the viewpoint of providing a battery configuration suitable for preventing contact between electrodes when forming an electrolyte seal portion for preventing seepage of an electrolyte solution from an electrolyte layer, As the electrolyte layer, a separator impregnated with an electrolytic solution or a polymer gel electrolyte (including a nonwoven fabric separator holding a polymer gel electrolyte) can be used. However, in the present invention, also regarding the polymer solid electrolyte, since the electrodes may come into contact with each other at the time of assembling the battery, it is similarly desirable to adopt a battery configuration suitable for preventing the electrodes from coming into contact with each other. . Therefore, in the present invention, depending on the purpose of use, (1) a polymer gel electrolyte (including a polymer gel electrolyte held in a nonwoven fabric separator), (2) a polymer solid electrolyte, or (3) an electrolyte solution Can be applied to any of the separators impregnated.
[0064]
(1) Polymer gel electrolyte (including non-woven fabric separator holding polymer gel electrolyte)
The polymer gel electrolyte is not particularly limited, and those used in conventional gel electrolyte layers can be appropriately used. Here, the gel electrolyte refers to a gel electrolyte in which an electrolyte is held in a polymer matrix. In the present invention, the difference between an all solid polymer electrolyte (also simply referred to as a polymer solid electrolyte) and a gel electrolyte is as follows.
[0065]
A gel electrolyte containing an all-solid polymer electrolyte such as polyethylene oxide (PEO) and an electrolyte used in a normal lithium ion battery.
[0066]
-A polymer electrolyte such as polyvinylidene fluoride (PVDF) having no lithium ion conductivity and having an electrolyte retained therein is also a gel electrolyte.
[0067]
The ratio of the polymer constituting the gel electrolyte (also referred to as a host polymer or a polymer matrix) and the electrolyte is wide, and if 100% by weight of the polymer is an all solid polymer electrolyte and 100% by weight of the electrolyte is a liquid electrolyte, the intermediate Every body is a gel electrolyte.
[0068]
The host polymer of the gel electrolyte is not particularly limited, and a conventionally known host polymer can be used. Preferably, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG) is used. ), Polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), poly (methyl methacrylate) (PMMA) and copolymers thereof are desirable, and the solvent is ethylene carbonate (EC), propylene Carbonate (PC), gamma-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof are preferred.
[0069]
The electrolytic solution (electrolyte salt and plasticizer) of the gel electrolyte is not particularly limited, and conventionally known ones can be used. More specifically, it may be any one that is usually used in a lithium ion battery. ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ Acid anion salts such as LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ Cyclic carbonates such as propylene carbonate, ethylene carbonate and the like containing at least one lithium salt (electrolyte salt) selected from organic acid anion salts such as N; chains such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate Ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane; lactones such as γ-butyrolactone; nitriles such as acetonitrile; Esters such as methyl propionate; amides such as dimethylformamide; and organic solvents (plasticizers) such as aprotic solvents in which at least one or more selected from methyl acetate and methyl formate are mixed. You can use what you used However, it is not limited to these.
[0070]
The proportion of the electrolyte solution in the gel electrolyte in the present invention is not particularly limited, but is preferably about several mass% to 98 mass% from the viewpoint of ionic conductivity and the like. The present invention is particularly effective for a gel electrolyte containing a large amount of an electrolytic solution in which the proportion of the electrolytic solution is 70% by mass or more.
[0071]
In the present invention, the amount of the electrolytic solution contained in the gel electrolyte may be made substantially uniform inside the gel electrolyte, or may be gradually reduced from the center to the outer periphery. . The former is preferable because the reactivity can be obtained in a wider range, and the latter is preferable in that the sealing property of the all solid polymer electrolyte portion in the outer peripheral portion with respect to the electrolytic solution can be improved. When the concentration is gradually reduced from the center toward the outer periphery, polyethylene oxide (PEO), polypropylene oxide (PPO), and a copolymer thereof having lithium ion conductivity are used as the host polymer. It is desirable.
[0072]
In the present invention, the electrolyte layer may be a nonwoven fabric separator in which a polymer gel electrolyte is held (see Examples described later).
[0073]
Here, the nonwoven fabric separator used to hold the polymer gel electrolyte is not particularly limited, and can be manufactured by entanglement of fibers to form a sheet. Further, spunbond or the like obtained by fusing fibers together by heating can also be used. In other words, any sheet may be used as long as the fibers are arranged in a web (thin cotton) or mat shape by an appropriate method, and are joined by an appropriate adhesive or the fusion force of the fibers themselves. The adhesive is not particularly limited as long as it has sufficient heat resistance at the temperature during production and use, and is stable without any reactivity or solubility even for the gel electrolyte. Instead, a conventionally known one can be used. The fibers used are not particularly limited. For example, conventionally known fibers such as cotton, rayon, acetate, nylon, polyester, polypropylene, polyethylene, and other polyolefins, polyimides, and aramids can be used. Depending on (eg, mechanical strength required for the electrolyte layer), they may be used alone or in combination. The bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. That is, if the bulk density of the nonwoven fabric is too large, the proportion of the non-electrolyte material in the electrolyte layer becomes too large, which may impair the ionic conductivity and the like in the electrolyte layer.
[0074]
The porosity of the nonwoven fabric separator is preferably 50 to 90%. When the porosity is less than 50%, the retention of the electrolytic solution is deteriorated, and when it exceeds 90%, the strength is insufficient. Furthermore, the thickness of the nonwoven fabric separator may be the same as that of the electrolyte layer described below, and is preferably 5 to 200 μm, and particularly preferably 10 to 100 μm. If the thickness is less than 5 μm, the retention of the electrolyte is deteriorated, and if it exceeds 200 μm, the resistance is increased.
[0075]
In addition, in the nonwoven fabric continuous body used as a spacer, an insulating material of the nonwoven fabric separator can be used. Also in the case of a continuous nonwoven fabric, one having a porosity of about 50 to 90% can be appropriately used.
[0076]
(2) Polymer solid electrolyte
The all solid polymer electrolyte is not particularly limited, and a conventionally known one can be used. Specifically, it is a layer composed of a polymer having ion conductivity, and the material is not limited as long as it exhibits ion conductivity. Examples of the all solid polymer electrolyte include known solid polymer electrolytes such as polyethylene oxide (PEO), polypropylene oxide (PPO), and a copolymer thereof. The solid polymer electrolyte contains a lithium salt in order to secure ion conductivity. As the lithium salt, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ Or a mixture thereof. However, it is not limited to these. Polyalkylene oxide-based polymers such as PEO and PPO are made of LiBF. ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ And other lithium salts. Further, by forming a crosslinked structure, excellent mechanical strength is exhibited.
[0077]
(3) Separator impregnated with electrolyte
As the electrolytic solution that can be impregnated into the separator, the same electrolytic solution (electrolyte salt and plasticizer) contained in the polymer gel electrolyte of the positive electrode layer described above can be used. Omitted.
[0078]
The separator is not particularly limited and may be a conventionally known separator. For example, a porous sheet (for example, a polyolefin-based microporous material) made of a polymer that absorbs and retains the electrolytic solution can be used. A separator, etc.) can be used. The polyolefin-based microporous separator having the property of being chemically stable to an organic solvent has an excellent effect that the reactivity with an electrolyte (electrolyte solution) can be suppressed to a low level.
[0079]
Examples of the material of the polymer include polyethylene (PE), polypropylene (PP), a laminate having a three-layer structure of PP / PE / PP, and polyimide.
[0080]
The thickness of the separator cannot be unambiguously defined because it varies depending on the intended use. However, in the case of a secondary battery for driving a motor such as an electric vehicle (EV) or a hybrid electric vehicle (HEV), a single layer thickness is used. Alternatively, the thickness is desirably 4 to 60 μm in a multilayer. When the thickness of the separator is within the above range, it is desirable to prevent short-circuiting caused by fine particles digging into the separator and to narrow the gap between the electrodes for high output. This has the effect of ensuring high output power. In the case where a plurality of batteries are connected, the electrode area increases. Therefore, it is desirable to use a thick separator in the above range in order to improve the reliability of the batteries.
[0081]
The diameter of the fine pores of the separator is desirably 1 μm or less at most (usually, the pore diameter is about several tens nm). When the average diameter of the micropores in the separator is within the above range, the separator is melted by heat and the "shutdown phenomenon", in which the micropores close, occurs quickly. There is an effect that is improved. In other words, when the battery temperature rises due to overcharging (in the event of an abnormality), the “shutdown phenomenon” in which the separator melts and the micropores close, which occurs quickly, causes the battery (electrode) from the positive electrode (+) to Li ions cannot pass through to the negative electrode (-) side, and cannot be charged any more. Therefore, overcharging cannot be performed, and overcharging is eliminated. As a result, the heat resistance (safety) of the battery can be improved, and gas can be prevented from being opened to open the heat-sealed portion (seal portion) of the battery exterior material. Here, the average diameter of the micropores of the separator is calculated as an average diameter obtained by observing the separator with a scanning electron microscope or the like and statistically processing a photograph thereof with an image analyzer or the like.
[0082]
The porosity of the separator is desirably 20 to 50%. When the porosity of the separator is within the above range, the output and reliability are reduced because the output is prevented from decreasing due to the resistance of the electrolyte (electrolyte solution) and the short circuit is prevented due to the fine particles penetrating through the pores (micropores). It has the effect of ensuring both sexes. Here, the porosity of the separator is a value obtained as a volume ratio from the density of the raw material resin and the density of the separator of the final product.
[0083]
The amount of the electrolyte impregnated in the separator may be impregnated up to the liquid retention capacity range of the separator, but may be beyond the liquid retention capacity range. This is because resin can be injected into the electrolyte seal portion to prevent the electrolyte solution from seeping out of the electrolyte layer, so that impregnation is possible as long as the electrolyte layer can retain the liquid. When the resin is injected into the electrolyte seal portion, the electrolyte solution is left with a liquid inlet (each one at a time) between each electrode, and is injected therefrom by a vacuum injection method or the like. The separator can be impregnated with the electrolytic solution by a conventionally known method, for example, by injecting a resin into the mouth and completely sealing the resin.
[0084]
The electrolyte layers (1) to (3) may be used together in one battery.
[0085]
Further, the polymer electrolyte may be contained in the polymer gel electrolyte layer, the positive electrode active material layer, and the negative electrode active material layer, but the same polymer electrolyte may be used, or different polymer electrolytes may be used depending on the layers. Good.
[0086]
Meanwhile, a host polymer for a polymer gel electrolyte which is preferably used at present is a polyether polymer such as PEO or PPO. For this reason, the oxidation resistance on the positive electrode side under high temperature conditions is weak. Therefore, when using a positive electrode agent having a high oxidation-reduction potential, which is generally used in a solution-based lithium ion battery, the capacity of the negative electrode is preferably smaller than the capacity of the positive electrode opposed via the polymer gel electrolyte layer. preferable. When the capacity of the negative electrode is smaller than the capacity of the opposed positive electrode, it is possible to prevent the positive electrode potential from excessively rising at the end of charging. In addition, the capacity of the positive electrode and the negative electrode can be obtained from the manufacturing conditions as a theoretical capacity at the time of manufacturing the positive electrode and the negative electrode. The capacity of the finished product may be measured directly by a measuring device.
[0087]
However, if the capacity of the negative electrode is smaller than the capacity of the opposite positive electrode, the potential of the negative electrode may be too low and the durability of the battery may be impaired. For example, the average charge voltage of one cell (single cell layer) is set to an appropriate value for the oxidation-reduction potential of the positive electrode active material to be used, and care is taken so that the durability does not decrease.
[0088]
The thickness of the electrolyte layer constituting the battery is not particularly limited. However, in order to obtain a compact bipolar battery, it is preferable to make the battery as thin as possible as long as the function as an electrolyte can be secured. The thickness of a general electrolyte layer is about 5 to 200 μm, preferably about 10 to 100 μm.
[0089]
[Positive and negative terminal plates]
The positive and negative electrode terminal plates may be used as needed. When used, it is better to have as thin as possible from the viewpoint of thinning in addition to having the function as a terminal, but since the laminated electrodes, electrolyte and current collector all have low mechanical strength, It is desirable to have enough strength to sandwich and support from above. Further, from the viewpoint of suppressing the internal resistance at the terminal portion, it can be said that the thickness of the positive electrode and negative electrode terminal plates is usually preferably about 0.1 to 2 mm.
[0090]
As the material of the positive electrode terminal and the negative electrode terminal plate, a material usually used in a lithium ion battery can be used. For example, aluminum, copper, titanium, nickel, stainless steel (SUS), alloys thereof, and the like can be used. It is preferable to use aluminum from the viewpoints of corrosion resistance, ease of production, economy, and the like.
[0091]
The materials of the positive electrode terminal plate and the negative electrode terminal plate may be the same or different. Further, these positive and negative electrode terminal plates may be formed by laminating different materials from each other in multiple layers.
[0092]
The positive and negative electrode terminal plates may have the same size as the current collector.
[0093]
[Positive and negative electrode leads]
As the positive and negative electrode leads, known leads that are usually used in lithium ion batteries can be used. In addition, since the part taken out of the battery exterior material (battery case) does not have a distance from the heat source of the automobile, it does not affect the automobile parts (especially electronic devices) by contacting them and causing a short circuit. It is preferable to coat with a heat-shrinkable heat-shrinkable tube or the like.
[0094]
[Battery exterior material (battery case)]
In order to prevent external shock and environmental degradation, the bipolar battery body must be entirely covered with a battery exterior material or battery case in order to prevent external impact and environmental degradation during use. (Not shown). From the viewpoint of weight reduction, a conventionally known battery package such as a polymer-metal composite laminate film or an aluminum laminate pack in which a metal (including an alloy) such as aluminum, stainless steel, nickel, or copper is coated with an insulator such as a polypropylene film. It is preferable that the battery laminate is housed and sealed by using a material and joining a part or all of its peripheral portion by heat fusion. In this case, the positive electrode and the negative electrode lead may have a structure sandwiched between the heat-sealed portions and exposed to the outside of the battery exterior material. In addition, the use of a polymer-metal composite laminate film or aluminum laminate pack with excellent thermal conductivity allows the heat to be efficiently transmitted from the heat source of the vehicle and quickly heats the inside of the battery to the battery operating temperature. preferable.
[0095]
Next, in the present invention, an assembled battery formed by connecting a plurality of the above bipolar batteries can be provided. That is, by using at least two or more bipolar batteries of the present invention and connecting them in series and / or in parallel to form an assembled battery, it is possible to respond to the demand for battery capacity and output for each purpose of use relatively inexpensively. It becomes possible to do.
[0096]
Specifically, for example, the above-mentioned N bipolar batteries are connected in parallel, and N parallel bipolar batteries are further connected in series to be stored in a metal or resin battery pack case to form a battery pack. . At this time, the number of series / parallel connected bipolar batteries is determined according to the purpose of use. For example, a large-capacity power supply such as an electric vehicle (EV) or a hybrid electric vehicle (HEV) may be combined so as to be applicable to a driving power supply of a vehicle requiring a high energy density and a high output density. Further, the positive electrode terminal and the negative electrode terminal for the assembled battery and the electrode lead of each bipolar battery may be electrically connected using a lead wire or the like. When the bipolar batteries are connected in series / parallel, they may be electrically connected using a suitable connecting member such as a spacer or a bus bar. However, the battery pack of the present invention should not be limited to the battery described here, and a conventionally known battery can be appropriately used. In addition, the assembled battery may be provided with various measuring devices and control devices according to the intended use, for example, a voltage measuring connector or the like may be provided to monitor the battery voltage. There is no particular limitation.
[0097]
According to the present invention, a vehicle equipped with the bipolar battery and / or the assembled battery as a driving power source can be provided. The bipolar battery and / or assembled battery of the present invention has various characteristics as described above, and is particularly a compact battery. For this reason, the present invention provides an electric vehicle and a hybrid vehicle which are suitable as a drive power source for a vehicle, for example, an electric vehicle or a hybrid electric vehicle, which has particularly strict requirements regarding energy density and output density, and which are excellent in fuel efficiency and running performance. it can. For example, it is convenient to mount a battery pack as a driving power source under a seat in the center of the body of an electric vehicle or a hybrid electric vehicle, because it is possible to widen a company space and a trunk room. However, the present invention is not limited thereto, and the battery pack or the battery can be installed under the floor of the vehicle, in a trunk room, an engine room, a roof, a hood of a hood, or the like. In the present invention, not only the assembled battery but also a bipolar battery may be mounted depending on the intended use, or the assembled battery and the bipolar battery may be mounted in combination. Further, as the vehicle on which the bipolar battery and / or the assembled battery of the present invention can be mounted as a driving power source, the above-described electric vehicle or hybrid electric vehicle is preferable, but is not limited thereto.
[0098]
The method for manufacturing the bipolar battery of the present invention is not particularly limited, and various conventionally known methods can be appropriately used. The following is a brief description. However, when stacking the electrodes, the method of arranging the spacers around the electrodes and then injecting resin around the electrodes to form the electrolyte seal portion is as already described with reference to FIG. The description here is omitted or simplified.
[0099]
(1) Application of positive electrode composition
First, an appropriate current collector is prepared. The positive electrode composition is usually obtained as a slurry (positive electrode slurry), and is applied to one surface of the current collector.
[0100]
The positive electrode slurry is a solution containing a positive electrode active material. As other components, a conductive auxiliary agent, a binder, a polymerization initiator, a raw material for an electrolyte (a polymer or a host polymer for a solid electrolyte, an electrolytic solution, etc.), a supporting salt (lithium salt), a slurry viscosity adjusting solvent, and the like are optionally included. That is, similarly to the solution-based lithium ion battery, the slurry for the positive electrode may optionally include a conductive auxiliary material, a raw material of an electrolyte, a supporting salt (lithium salt), a slurry viscosity adjusting solvent, a polymerization initiator, and the like, in addition to the negative electrode active material. It can be manufactured by mixing the materials containing at a predetermined ratio.
[0101]
When a polymer gel electrolyte is used for the electrolyte layer, it is sufficient that a conventionally known binder for binding the positive electrode active material fine particles to each other, a conductive auxiliary material for increasing electron conductivity, a solvent, and the like are included. The raw material does not need to contain the host polymer, the electrolytic solution, the lithium salt, and the like. The same applies when a separator in which the electrolyte layer is impregnated with the electrolyte is used.
[0102]
Examples of the polymer raw material for the electrolyte (host polymer as the raw material for the polymer gel electrolyte or the polymer raw material for the polymer solid electrolyte) include PEO, PPO, and copolymers thereof, and a crosslinkable functional group ( (A carbon-carbon double bond). By cross-linking the polymer electrolyte using the cross-linkable functional group, the mechanical strength is improved.
[0103]
As for the positive electrode active material, the conductive additive, the binder, and the lithium salt, the compounds described above can be used.
[0104]
The polymerization initiator needs to be selected according to the compound to be polymerized. For example, benzyldimethyl ketal is used as a photopolymerization initiator, and azobisisobutyronitrile is used as a thermal polymerization initiator.
[0105]
The solvent such as NMP is selected according to the type of the positive electrode slurry.
[0106]
The amounts of the positive electrode active material, the lithium salt, and the conductive additive may be adjusted according to the purpose of the bipolar battery or the like, and may be generally used. The amount of the polymerization initiator to be added is determined according to the number of crosslinkable functional groups contained in the polymer material. Usually, it is about 0.01 to 1% by mass with respect to the polymer raw material.
[0107]
(2) Formation of positive electrode layer
The current collector coated with the positive electrode slurry is dried to remove the contained solvent. At the same time, depending on the slurry for the positive electrode, a cross-linking reaction may be advanced to increase the mechanical strength of the solid polymer electrolyte. For drying, a vacuum dryer or the like can be used. Drying conditions are determined according to the applied slurry for the positive electrode and cannot be uniquely defined, but are usually from 40 to 150 ° C. for 5 minutes to 20 hours.
[0108]
(3) Application of composition for negative electrode
A negative electrode composition (negative electrode slurry) containing a negative electrode active material is applied to the surface opposite to the surface on which the positive electrode layer is applied.
[0109]
A negative electrode composition (negative electrode slurry) containing a negative electrode active material is applied to the surface opposite to the surface on which the positive electrode layer is applied.
[0110]
The negative electrode slurry is a solution containing a negative electrode active material. Other components optionally include a conductive additive, a binder, a polymerization initiator, (a polymer or a host polymer for a solid electrolyte, an electrolytic solution, etc.), a supporting salt (lithium salt), a slurry viscosity adjusting solvent, and the like. The raw materials used and the amounts added are the same as those described in the section of “(1) Application of positive electrode composition”, and thus description thereof is omitted here.
[0111]
(4) Formation of negative electrode layer
The current collector coated with the negative electrode slurry is dried to remove the contained solvent. At the same time, depending on the slurry for the negative electrode, the crosslinking reaction may be advanced to increase the mechanical strength of the polymer gel electrolyte. By this operation, a bipolar electrode is completed. For drying, a vacuum dryer or the like can be used. The drying conditions are determined according to the applied slurry for the negative electrode, and cannot be uniquely defined, but are usually at 40 to 150 ° C. for 5 minutes to 20 hours. By such a drying process, a negative electrode layer (electrode forming portion) is formed on the current collector.
[0112]
(5) Formation of electrolyte layer
When the polymer solid electrolyte layer is used, the polymer solid electrolyte layer is produced by, for example, curing a solution prepared by dissolving a raw material polymer of the polymer solid electrolyte, a lithium salt, or the like in a solvent such as NMP. When a polymer gel electrolyte layer is used, for example, as a raw material of the polymer gel electrolyte, a pre-gel solution comprising a host polymer and an electrolyte solution, a lithium salt, a polymerization initiator, and the like are simultaneously heated and dried under an inert atmosphere. It is produced by polymerizing (promoting a crosslinking reaction). When using a polymer gel electrolyte layer in which a polymer gel electrolyte is held in a nonwoven fabric separator, a host polymer and an electrolyte, a lithium salt, and a polymerization initiator may be used in the nonwoven fabric separator, for example, as raw materials for the polymer gel electrolyte. It is manufactured by impregnating a pregel solution comprising an agent and the like, and simultaneously heating and drying in an inert atmosphere and simultaneously polymerizing (promoting a crosslinking reaction) (see Examples described later).
[0113]
For example, the prepared solution or pregel solution is applied on the electrode (positive electrode and / or negative electrode), and an electrolyte layer having a predetermined thickness or a part thereof (an electrolyte membrane having a thickness of about half the electrolyte layer thickness) is formed. Form. After that, the electrode on which the electrolyte layer (membrane) is laminated is cured or heated and dried in an inert atmosphere and simultaneously polymerized (promoting a crosslinking reaction), thereby increasing the mechanical strength of the electrolyte and producing the electrolyte layer (membrane). A film is formed (completed).
[0114]
Alternatively, an electrolyte layer laminated between the electrodes or a part thereof (an electrolyte membrane having a thickness of about half the electrolyte layer thickness) is separately prepared. An electrolyte layer (membrane) or a polymer gel electrolyte layer (membrane) obtained by holding a polymer gel electrolyte in a non-woven fabric separator is prepared by applying the above solution or pregel solution on a suitable film such as a PET film, and applying an inert atmosphere. Or by pre-polymerization (promoting the cross-linking reaction) at the same time as curing or heating and drying, or impregnating the above solution or pregel solution with a suitable nonwoven fabric separator such as PP and curing or heating under an inert atmosphere. It is produced by polymerizing (promoting the crosslinking reaction) simultaneously with drying.
[0115]
For curing or heat drying, a vacuum dryer (vacuum oven) or the like can be used. The conditions of the heat drying are determined according to the solution or the pregel solution and cannot be uniquely defined, but are usually at 30 to 110 ° C. for 0.5 to 12 hours.
[0116]
The thickness of the electrolyte layer (membrane) can be controlled using a spacer or the like. When a photopolymerization initiator is used, it is poured into a light-transmitting gap and irradiated with ultraviolet rays using an ultraviolet irradiation device capable of drying and photopolymerization, thereby photopolymerizing the polymer in the electrolyte layer and performing a crosslinking reaction. It is advisable to proceed the film formation. However, it is a matter of course that the present invention is not limited to this method. Depending on the type of the polymerization initiator, radiation polymerization, electron beam polymerization, thermal polymerization, and the like are properly used.
[0117]
Further, since the film used above may be heated to about 80 ° C. during the manufacturing process, the film has sufficient heat resistance at the temperature, and has no reactivity with the solution or the pregel solution. It is desirable to use a material excellent in releasability from the necessity of peeling and removing with, for example, polyethylene terephthalate (PET), a polypropylene film and the like can be used, but it is not limited thereto.
[0118]
The width of the electrolyte layer is often slightly smaller than the current collector size of the bipolar electrode.
[0119]
The composition of the above solution or pregel solution and the amount thereof should be appropriately determined according to the purpose of use.
[0120]
The separator impregnated with the electrolytic solution has the same configuration as the electrolyte layer used for the conventional non-bipolar type solution-based bipolar battery, and conventionally known various manufacturing methods, for example, a separator impregnated with the electrolytic solution is used. Since it can be manufactured by a method of sandwiching and stacking between bipolar electrodes or a vacuum injection method, a detailed description thereof will be omitted below.
[0121]
(6) Lamination of bipolar electrode and electrolyte layer
{Circle around (1)} In the case of a bipolar electrode having an electrolyte layer (membrane) formed on one or both sides, sufficiently heat and dry under a high vacuum, and then form a plurality of electrodes having the electrolyte layer (membrane) in an appropriate size. The bipolar battery main body (electrode laminate) is manufactured by cutting out the individual pieces and directly attaching the cut out electrodes.
[0122]
(2) In the case where the bipolar electrode and the electrolyte layer (membrane) are separately manufactured, they are sufficiently heated and dried under a high vacuum, and then each of the bipolar electrode and the electrolyte layer (membrane) is cut into a plurality of appropriate sizes. . A predetermined number of the cut-out bipolar electrodes and the electrolyte layer (membrane) are attached to each other to produce a bipolar battery main body (electrode laminate).
[0123]
The number of layers of the electrode stack is determined in consideration of battery characteristics required for a bipolar battery. In the outermost layer on the positive electrode side, an electrode in which only the positive electrode layer is formed on the current collector is arranged. In the outermost layer on the negative electrode side, an electrode in which only the negative electrode layer is formed on the current collector is arranged. The step of obtaining a bipolar battery by laminating a bipolar electrode and an electrolyte layer (membrane) or laminating an electrode on which an electrolyte layer (membrane) is formed is difficult from the viewpoint of preventing moisture and the like from being mixed into the battery. It is preferable to carry out under an active atmosphere. For example, a bipolar battery is preferably manufactured in an argon atmosphere or a nitrogen atmosphere.
[0124]
(7) Installation of spacer
In the present invention, as described above, when the bipolar electrode and the polymer electrolyte layer are bonded and laminated, for example, as shown in FIGS. The spacer 23 having a shape is adhered and arranged with an adhesive. Alternatively, the continuous body spacer of FIG. 6 or a non-woven fabric is temporarily fixed with an adhesive or glue. Note that this step may be performed at this stage as described above, or may be set before forming the positive electrode layer or the negative electrode layer in advance.
[0125]
(8) Formation of electrolyte seal (insulation layer)
The four sides of the outer peripheral portion of the electrode laminate are separated from the outer side by a predetermined width (for example, a width of about 10 mm; W in FIG. 5). ₁ For example, the sealing resin is immersed in an epoxy resin (precursor solution) as a sealing portion resin, and then the epoxy resin is cured to form an electrolyte sealing portion. In the present invention, it is needless to say that the present invention is not limited to these, and a conventionally known resin injection technique can be appropriately used. Thereby, the spacer can be completely taken into the resin of the electrolyte seal portion, and a seal portion without leakage can be formed.
[0126]
(7) Packing (completion of battery)
Finally, a positive electrode terminal plate and a negative electrode terminal plate are respectively disposed on both outermost electron conductive layers of the bipolar battery body (battery laminate), and a positive electrode lead and a negative electrode lead are further provided on the positive electrode terminal plate and the negative electrode terminal plate. Are joined (electrically connected) and taken out. The method for joining the positive electrode lead and the negative electrode lead is not particularly limited, but ultrasonic welding or the like having a low joining temperature can be suitably used, but is not limited to this. A known joining method can be appropriately used.
[0127]
The entire battery stack is sealed with a battery exterior material or a battery case in order to prevent external impact and environmental degradation, thereby completing a bipolar battery. At this time, the positive electrode lead, the negative electrode lead, and the connector (or the wiring portion thereof) are sealed, and a part thereof is taken out of the battery (see FIG. 3). The material of the battery exterior material (battery case) is preferably a metal (aluminum, stainless steel, nickel, copper, or the like) whose inner surface is covered with an insulator such as a polypropylene film.
[0128]
【Example】
The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples.
[0129]
Example 1 (example of the first embodiment)
<Formation of electrode>
1. Positive electrode layer
Spinel LiMn having an average particle diameter of 2 μm as a positive electrode active material ₂ O ₄ [85% by mass], acetylene black [5% by mass] as a conductive aid, PVDF [10% by mass] as a binder, and N-methyl-2-pyrrolidone (NMP) as a slurry viscosity adjusting solvent (NMP is (Because it is removed by volatilization, an appropriate amount was added so as to obtain an appropriate slurry viscosity instead of the constituent material of the electrode.) A material composed of the above ratio (indicated by a ratio converted by a component excluding the slurry viscosity adjusting solvent). To prepare a positive electrode slurry.
[0130]
The positive electrode slurry was applied to one side of a SUS foil (thickness: 20 μm) as a current collector, placed in a vacuum oven, and dried at 120 ° C. for 10 minutes to form a positive electrode layer having a dry thickness of 40 μm.
[0131]
2. Negative electrode layer
A material composed of hard carbon [90% by mass] as a negative electrode active material, PVDF [10% by mass] as a binder, and NMP (an appropriate amount was added so as to have an appropriate slurry viscosity) as a slurry viscosity adjusting solvent was used in the above ratio (slurry). A negative electrode slurry was prepared by mixing with the ratio excluding the viscosity adjusting solvent.
[0132]
The negative electrode slurry was applied to the opposite surface of the SUS foil on which the positive electrode layer was formed, placed in a vacuum oven, and dried at 120 ° C. for 10 minutes to form a negative electrode layer having a dry thickness of 40 μm.
[0133]
A bipolar electrode was formed by forming a positive electrode layer and a negative electrode layer on both sides of a SUS foil as a current collector (see FIG. 1).
[0134]
<Formation of gel electrolyte layer>
A nonwoven fabric made of PP having a thickness of 50 μm (porosity: 60%) was used as a separator.
[0135]
In the separator, a copolymer of polyethylene oxide and polypropylene oxide (a copolymer having a copolymerization ratio of 5: 1 and a weight average molecular weight of 8000) [10% by mass] was used as a host polymer and an electrolyte solution EC + DMC (1: 1). 3 (volume ratio)) and lithium salt LiBF at 1.0M ₄ [90% by mass] and a pregel solution composed of AIBN [0.1% by mass with respect to the host polymer] as a polymerization initiator are immersed, and thermally polymerized at 90 ° C for 1 hour in an inert atmosphere. As a result, a gel electrolyte layer in which the gel electrolyte was held by the nonwoven fabric separator was formed. The thickness of the obtained gel electrolyte layer was 50 μm, and was not thicker than the nonwoven fabric separator.
[0136]
<Formation of bipolar battery>
The bipolar electrode and the gel electrolyte layer were laminated so that the positive electrode layer and the negative electrode layer of the electrode sandwiched the gel electrolyte layer.
[0137]
When laminating, as shown in FIGS. 5A and 5B, the periphery of the electrode (the width W of the periphery) ₁ Was 8 mm. ), A columnar (5 mm diameter) PP spacer having a thickness (height) of 100 μm was laminated while being disposed at 12 locations at appropriate intervals. The spacer was temporarily fixed with glue.
[0138]
<Formation of seal part>
Four sides of an outer peripheral portion of a 50 μm-thick polypropylene nonwoven fabric were immersed in an epoxy resin as a resin for electrolyte sealing with a width of 10 cm from the outer edge, and then the epoxy resin was cured to form an electrolyte seal portion. (See FIG. 5C).
[0139]
After laminating five layers (equivalent to five cells), the battery laminate was sealed with a laminate pack (aluminum laminated with a polypropylene film; battery exterior material) to form a bipolar battery.
[0140]
Comparative Example 1
As Comparative Example 1, five layers (equivalent to five cells) were laminated in the same manner as in Example 1 except that the electrolyte seal portion and the spacer were not provided, and then the battery laminate was laminated with a laminate pack (aluminum laminated with a polypropylene film). (Battery exterior material) to form a bipolar battery.
[0141]
<Evaluation>
In Example 1, even when ten battery samples were manufactured, generation of a defective battery due to a short circuit due to contact between terminals was not recognized in the manufacturing process. For confirmation, a charge / discharge cycle test of the battery of Example 1 was performed. The charge / discharge cycle test was performed at 25 ° C., and the charge / discharge current value was 0.5 CA.
[0142]
In the bipolar battery of Example 1, it was confirmed that the voltage of each cell layer was maintained even after more than 50 cycles, and that no short circuit was caused by contact between terminals.
[0143]
In the case of the battery of Comparative Example 1 having no spacer, when ten battery samples were manufactured, a short circuit due to the contact of the current collector foil during the manufacturing process, or a liquid junction where the electrolyte leaked out and the electrolytes came into contact with each other was obtained. It was recognized that defective batteries were generated in all 10 batteries.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view schematically showing a basic structure of a bipolar electrode constituting a bipolar battery of the present invention.
FIG. 2 is a schematic cross-sectional view schematically showing a basic structure of a unit cell layer (single cell) constituting the bipolar battery of the present invention.
FIG. 3 is a schematic sectional view schematically showing a basic structure of a bipolar battery of the present invention.
FIG. 4 is a schematic diagram schematically showing a basic configuration of a bipolar battery of the present invention.
FIG. 5A is a plan view of an electrode laminate including a plurality of columnar spacers (a current collector in the uppermost layer is not shown), and FIG. 5B is a plan view of the electrode laminate. FIG. 6 is a schematic side view of the electrode laminate of FIG.
6 (a) is a side view schematically showing one of the embodiments of a spacer used in the present invention, and FIG. 6 (b) is a plan view of the spacer of FIG. 6 (a). FIG.
FIG. 7 is an enlarged plan view of a corner portion in a state where an electrolyte seal portion is formed around a unit cell layer of the electrode laminate of FIG. 5A (a current collector in the uppermost layer is not shown) .
FIG. 8A is a schematic side view of an electrode stack using a spacer. FIG. 8 (b) shows a state before immersing the electrode periphery of the electrode stack in a resin (precursor) as a method of forming an electrolyte seal around the cell layer of the outer electrode stack using spacers. It is the schematic diagram which represented typically. FIG. 8C is a schematic diagram schematically showing a state in which the unit cell layers are electrically insulated by the spacers even when the periphery of the electrodes of the electrode stack is immersed in a resin (precursor).
FIG. 9A is a schematic side view of an electrode laminate without using a spacer. FIG. 9B schematically shows a state before immersing the electrode periphery of the electrode stack in a resin (precursor) as a method of forming an electrolyte seal around the cell layer of the outer electrode stack. It is a schematic diagram. FIG. 9C is a schematic diagram schematically showing a state in which the unit cell layers are electrically short-circuited by immersing the periphery of the electrode of the electrode stack in a resin (precursor).
[Explanation of symbols]
1 ... current collector (metal foil)
2 ... Positive electrode layer,
3: Negative electrode layer,
4 ... Electrolyte layer (electrolyte membrane),
5 ... Bipolar electrode,
5a: an electrode having a positive electrode layer disposed only on one required surface of the current collector;
5b: an electrode in which a negative electrode layer is arranged on only one required surface of the current collector,
6 ... unit cell layer (single cell),
7 ... electrode laminate,
8 Positive electrode lead,
9 ... negative electrode lead,
10. Battery exterior material,
11 ... bipolar battery,
21 ... electrolyte seal part,
23 ... spacer,
23a ... a continuum of spacers,
25 ... opening,
31 ... sealing resin precursor,
W ₁ ... the width of the electrolyte seal,
W ₂ ... spacer width,
W ₃ ... The width of the continuum spacer.

Claims (8)

In a bipolar lithium ion secondary battery in which a positive electrode is formed on one surface of a current collector and a bipolar electrode having a negative electrode formed on the other surface, a plurality of bipolar electrodes are stacked in series with an electrolyte layer interposed therebetween,
A bipolar battery, wherein a spacer for maintaining a space between electrodes is provided in an electrolyte seal portion on a side surface of the electrode. 2. The bipolar battery according to claim 1, wherein the spacer is completely incorporated into a resin of an electrolyte seal portion. 3. The method for manufacturing a bipolar battery according to claim 1, wherein when laminating the electrodes, a spacer is arranged around the electrodes, and thereafter, a resin is injected around the electrodes to form an electrolyte seal portion. Using a lithium-transition metal composite oxide as the positive electrode active material,
The bipolar battery according to any one of claims 1 to 3, wherein carbon or a lithium-transition metal composite oxide is used as the negative electrode active material. The bipolar battery according to any one of claims 1 to 4, wherein a separator or a polymer gel electrolyte impregnated with an electrolytic solution is used for the electrolyte layer. The bipolar battery according to any one of claims 1 to 4, wherein a solid polymer is used for the polymer electrolyte. An assembled battery comprising a plurality of the bipolar batteries according to claim 1 connected to each other. A vehicle comprising the bipolar battery according to claim 1 and / or the battery pack according to claim 7 as a driving power source.

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